1. Field
The following description relates to acousto-optic devices having a wide range of diffraction angle, optical scanners, light modulators, and display apparatuses using the acousto-optic devices, and, for example, to acousto-optic devices capable of increasing a diffraction angle range or adjusting diffraction angle characteristics of an output light by using a strong anisotropic refractive index that generates around a photonic band gap of a photonic crystal, optical scanners, light modulators, and display apparatuses using the acousto-optic devices.
2. Description of Related Art
The acousto-optic effect serves to regularly change a refractive index of light in a medium by changing degrees of compression and rarefaction of the medium using sonic waves or ultrasonic waves. The acousto-optic effect may enable the medium to function as a phase grating. Thus, light that is incident to the medium may be diffracted according to the acousto-optic effect.
In addition, the medium that diffracts the incident light according to the acousto-optic effect is generally referred to as an acousto-optic medium. An intensity of light diffracted by the acousto-optic medium and angle at which the light is diffracted by the acousto-optic medium may vary respectively depending on intensity and frequency of sound waves. Therefore, an acousto-optic device, in which a sound wave generator (e.g., an ultrasonic wave generator) is mounted on a surface of the acousto-optic medium, may be applied in a light modulator to modulate an amplitude of the light, or an optical scanner to deviate the light.
However, a natural acousto-optic medium may be limited with respect to optical anisotropy and acousto-optic transformation rates. Therefore, acousto-optic devices using the natural acousto-optic medium may be limited with respect to the diffraction angle of the output light. That is, in related acousto-optic devices using the natural acousto-optic medium, a width of a range of the diffraction angle is insufficient to provide adequate modulation or deviation of the output light.
Therefore, when related acousto-optic devices are used in optical scanners, light modulators, displays, and other similar systems, an additional optical system is necessary in order to compensate for the limited diffraction angle range. The inclusion of the additional optical system may increase the size of the above-referenced systems or serve to degrade resolution in the above-referenced systems. Accordingly, there is a need for developing acousto-optic devices having increased diffraction angle ranges. Research is actively being conducted involving the structuring of the acousto-optic medium in various shapes within acousto-optic devices.